Cheng Zhe, Huang Yu-Ju, Zahiri Beniamin, Kwon Patrick, Braun Paul V, Cahill David G
Department of Materials Science and Engineering and Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
Phys Chem Chem Phys. 2024 Feb 22;26(8):6708-6716. doi: 10.1039/d3cp05998g.
The coupled transport of charge and heat provide fundamental insights into the microscopic thermodynamics and kinetics of materials. We describe a sensitive ac differential resistance bridge that enables measurements of the temperature difference on two sides of a coin cell with a resolution of better than 10 μK. We use this temperature difference metrology to determine the ionic Peltier coefficients of symmetric Li-ion electrochemical cells as a function of Li salt concentration, solvent composition, electrode material, and temperature. The Peltier coefficients Π are negative, , heat flows in the direction opposite to the drift of Li ions in the applied electric field, large, -Π > 30 kJ mol, and increase with increasing temperature at > 300 K. The Peltier coefficient is approximately constant on time scales that span the characteristic time for mass diffusion across the thickness of the electrolyte, suggesting that heat of transport plays a minor role in comparison to the changes in partial molar entropy of Li at the interface between the electrode and electrolyte. Our work demonstrates a new platform for studying the non-equilibrium thermodynamics of electrochemical cells and provides a window into the transport properties of electrochemical materials through measurements of temperature differences and heat currents that complement traditional measurements of voltages and charge currents.
电荷与热的耦合输运为深入了解材料的微观热力学和动力学提供了基础。我们描述了一种灵敏的交流差分电阻桥，它能够测量硬币电池两侧的温差，分辨率优于10 μK。我们利用这种温差计量法来确定对称锂离子电化学电池的离子珀尔帖系数，该系数是锂盐浓度、溶剂组成、电极材料和温度的函数。珀尔帖系数Π为负，即热量流动方向与外加电场中锂离子的漂移方向相反，其值较大，-Π > 30 kJ/mol，且在温度高于300 K时随温度升高而增大。在跨越电解质厚度的质量扩散特征时间的时间尺度上，珀尔帖系数近似恒定，这表明与电极和电解质界面处锂的偏摩尔熵变化相比，输运热起的作用较小。我们的工作展示了一个研究电化学电池非平衡热力学的新平台，并通过测量温差和热流为了解电化学材料的输运性质提供了一个窗口，这些测量补充了传统的电压和电荷电流测量。
